In most hotels, restaurants and catering operations, automatic dishwashers are widely used to quickly clean and sanitise plating and utensils used in food preparation and presentation. As such, dishwashing equipment represents a critical control point in most HACCP plans and in the overall effort to maintain hygienic conditions in food preparation areas.
To date, uniform standards regarding the hygiene of dishwashing equipment used in commercial settings have not been widely available. Therefore, food processing operations generally rely on the specifications and recommendations of dishwasher manufacturers for operation and maintenance procedures that will result in acceptable hygienic performance. However, that situation may change in the near future with the release of DIN SPEC 10534, “Food Hygiene - Commercial dishwashing - Hygiene requirements, testing.”
Published in 2012 by the German Institute for Standardisation, DIN 10534 is a draft standard that specifies hygiene requirements related to the design, construction and operation of commercial dishwashers. DIN 10534 effectively combines the requirements of three existing DIN standards, DIN 10510, DIN 10511 and DIN 10512, and includes detailed information on the care and maintenance of dishwasher equipment as well as methods that can be used to test hygienic operation. This comprehensive approach to dishwasher hygiene means that DIN 10534 is likely to serve as the foundation for an internationally-accepted standard for commercial dishwashers.
In the meantime, DIN 10534 is an excellent source of best practices to ensure the hygienic operation of dishwasher equipment used in commercial food preparation settings. Specifically, the standard identifies requirements in the following areas:
Microbiological requirements—In addition to ensuring that dishware is visibly clean and dry upon the completion of the cleaning cycle, commercial dishwashers must also achieve a level of disinfection performance as specified in Table 1—Microbiological requirements. Table 1 details aerobic counts for various types of dishware and reusable crates and containers, as well as bacterial reduction levels for bioindicators placed inside the machine.
Operating temperatures—DIN 10534 standardises acceptable operating temperature ranges for five distinctive points in the dishwashing process, including fresh water pre-wash zone, pre-wash zone, detergent-circulating tank, auxiliary rinse zone and fresh water rinse.
Contact time—For each phase of the dishwashing process, DIN 10534 sets a minimum contact time of 90 seconds for single tank dishwashers and two minutes for multi-tank dishwashers in order to obtain a hygienically safe result.
Dishwasher cleaning—The standard requires that a dishwasher be thoroughly cleaned at the end of each operating period, which should include emptying the tanks, cleaning the strainer systems, the dishwasher interior and all water jet nozzles. In addition, all cutlery-soaking containers and waste containers must be emptied and cleaned at least once a day.
Operating records—DIN 10534 requires an operator to maintain a daily operation logbook that records the start and end times of operating periods, operating temperatures, any malfunctions that occurred as well as any repairs or maintenance that was performed.
Inspection and testing—Finally, the standard specifies both daily and periodic inspection and testing to ensure that a dishwasher is operating hygienically. Daily inspection includes visual inspection and checks for temperature, water quality and overall cleanliness. Periodic inspections also include testing to determine surface total area aerobic count on dishware and total aerobic count in the detergent solution. Where applicable, testing with bioindicators is also prescribed.
As previously noted, DIN 10534’s comprehensive approach to maintaining the hygienic performance of commercial dishwashing equipment is likely to serve as the basis for subsequent standards development efforts in this area. Therefore, adopting the practices prescribed in DIN 10534 not only contributes to the effectiveness of overall hygiene practices in commercial food preparation areas, but can help hotels, restaurants and caterers achieve state-of-the-art performance in overall food safety.